Immunization Programs and Vaccine Preventable Diseases Service (Skowronski, Kaweski, Chuang, Kim), BC Centre for Disease Control; School of Population and Public Health (Skowronski, Henry, Smolina), University of British Columbia; Data and Analytic Services (Irvine, Smolina), BC Centre for Disease Control, Vancouver, BC; Faculty of Health Sciences (Irvine), Simon Fraser University, Burnaby, BC; Public Health Laboratory (Sabaiduc, Sekirov), BC Centre for Disease Control; Department of Pathology and Laboratory Medicine (Reyes, Sekirov), University of British Columbia, Vancouver, BC; LifeLabs (Reyes), Burnaby, BC; Ministry of Health (Henry), Office of the Provincial Health Officer, Victoria, BC
Immunization Programs and Vaccine Preventable Diseases Service (Skowronski, Kaweski, Chuang, Kim), BC Centre for Disease Control; School of Population and Public Health (Skowronski, Henry, Smolina), University of British Columbia; Data and Analytic Services (Irvine, Smolina), BC Centre for Disease Control, Vancouver, BC; Faculty of Health Sciences (Irvine), Simon Fraser University, Burnaby, BC; Public Health Laboratory (Sabaiduc, Sekirov), BC Centre for Disease Control; Department of Pathology and Laboratory Medicine (Reyes, Sekirov), University of British Columbia, Vancouver, BC; LifeLabs (Reyes), Burnaby, BC; Ministry of Health (Henry), Office of the Provincial Health Officer, Victoria, BC.
CMAJ. 2023 Oct 30;195(42):E1427-E1439. doi: 10.1503/cmaj.230721.
Population-based cross-sectional serosurveys within the Lower Mainland, British Columbia, Canada, showed about 10%, 40% and 60% of residents were infected with SARS-CoV-2 by the sixth (September 2021), seventh (March 2022) and eighth (July 2022) serosurveys. We conducted the ninth (December 2022) and tenth (July 2023) serosurveys and sought to assess risk of severe outcomes from a first-ever SARS-CoV-2 infection during intersurvey periods.
Using increments in cumulative infection-induced seroprevalence, population census, discharge abstract and vital statistics data sets, we estimated infection hospitalization and fatality ratios (IHRs and IFRs) by age and sex for the sixth to seventh (Delta/Omicron-BA.1), seventh to eighth (Omicron-BA.2/BA.5) and eighth to ninth (Omicron-BA.5/BQ.1) intersurvey periods. As derived, IHR and IFR estimates represent the risk of severe outcome from a first-ever SARS-CoV-2 infection acquired during the specified intersurvey period.
The cumulative infection-induced seroprevalence was 74% by December 2022 and 79% by July 2023, exceeding 80% among adults younger than 50 years but remaining less than 60% among those aged 80 years and older. Period-specific IHR and IFR estimates were consistently less than 0.3% and 0.1% overall. By age group, IHR and IFR estimates were less than 1.0% and up to 0.1%, respectively, except among adults aged 70-79 years during the sixth to seventh intersurvey period (IHR 3.3% and IFR 1.0%) and among those aged 80 years and older during all periods (IHR 4.7%, 2.2% and 3.5%; IFR 3.3%, 0.6% and 1.3% during the sixth to seventh, seventh to eighth and eighth to ninth periods, respectively). The risk of severe outcome followed a J-shaped age pattern. During the eighth to ninth period, we estimated about 1 hospital admission for COVID-19 per 300 newly infected children younger than 5 years versus about 1 per 30 newly infected adults aged 80 years and older, with no deaths from COVID-19 among children but about 1 death per 80 newly infected adults aged 80 years and older during that period.
By July 2023, we estimated about 80% of residents in the Lower Mainland, BC, had been infected with SARS-CoV-2 overall, with low risk of hospital admission or death; about 40% of the oldest adults, however, remained uninfected and at highest risk of a severe outcome. First infections among older adults may still contribute substantial burden from COVID-19, reinforcing the need to continue to prioritize this age group for vaccination and to consider them in health care system planning.
在加拿大卑诗省低陆平原进行的基于人群的横断面血清学调查显示，第六次（2021 年 9 月）、第七次（2022 年 3 月）和第八次（2022 年 7 月）血清学调查中，分别有 10%、40%和 60%的居民感染了 SARS-CoV-2。我们进行了第九次（2022 年 12 月）和第十次（2023 年 7 月）血清学调查，并试图评估在两次调查之间感染 SARS-CoV-2 后出现严重后果的风险。
利用累积感染诱导的血清阳性率、人口普查、出院摘要和生命统计数据集，我们按年龄和性别估计了第六次到第七次（Delta/Omicron-BA.1）、第七次到第八次（Omicron-BA.2/BA.5）和第八次到第九次（Omicron-BA.5/BQ.1）两次调查之间的感染住院和死亡率（IHR 和 IFR）。估计的 IHR 和 IFR 代表在特定的两次调查期间首次感染 SARS-CoV-2 后出现严重后果的风险。
截至 2022 年 12 月，累积感染诱导的血清阳性率为 74%，2023 年 7 月为 79%，50 岁以下成年人的阳性率超过 80%，但 80 岁以上成年人的阳性率仍低于 60%。特定时期的 IHR 和 IFR 估计值总体上均低于 0.3%和 0.1%。按年龄组划分，IHR 和 IFR 估计值均低于 1.0%，最高为 0.1%，除了 60-69 岁年龄组在第六次到第七次两次调查期间（IHR 3.3%和 IFR 1.0%）和 80 岁及以上年龄组在所有期间（IHR 4.7%、2.2%和 3.5%；IFR 3.3%、0.6%和 1.3%，分别在第六次到第七次、第七次到第八次和第八次到第九次期间）。严重后果的风险呈现出 J 型年龄模式。在第八次到第九次调查期间，我们估计每 300 名 5 岁以下新感染儿童中就有 1 人因 COVID-19 住院，而每 30 名 80 岁及以上新感染成年人中就有 1 人住院，该期间儿童中没有 COVID-19 死亡病例，但每 80 名新感染的 80 岁及以上成年人中就有 1 人死亡。
截至 2023 年 7 月，我们估计卑诗省低陆平原约 80%的居民已整体感染 SARS-CoV-2，住院或死亡的风险较低；然而，约 40%的最年长成年人仍未感染，面临最高的严重后果风险。老年人中的初次感染仍可能对 COVID-19 造成重大负担，这突显了继续为这一年龄组优先接种疫苗并在医疗保健系统规划中考虑这一年龄组的重要性。
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